1. Technical Field
This invention generally relates to a vehicle closure apparatus and, more particularly, to a closure apparatus having multiple doors with concealed hinges for covering a single opening in a vehicle body.
2. Discussion
One advantage of having a large vehicle, such as a van, minivan, or sport utility vehicle, is that a large cargo area is available for carrying cargo. In order to fully utilize this cargo area, a large opening is generally provided in the vehicle body so that objects which would not fit through the traditional door openings of a vehicle can be loaded into the cargo area. A noted disadvantage of having a large opening in the vehicle body is the fact that a large door must be provided to cover the opening. Traditionally within the automotive industry these doors, or closures, as they are often referred to, have been placed at the rear of the vehicle and are generally a one or two piece design.
Initially, two-piece designs were used in which there were either two horizontal doors or two vertical doors. Typically, vertical doors were utilized on cargo vans or full sized passenger vans while horizontal doors were utilized on station wagons and were typically a clam shell type opening.
One-piece doors, typically referred to as a liftgate, have been used with increasing frequency on sport utility type vehicles and minivans. The liftgate is typically hinged along the top portion of the door which generally coincides with the roof line at the rear of the vehicle. The liftgate typically extends from the roof line to a point just above the rear bumper and pivots upwardly so that the liftgate is overhead when fully opened.
Several disadvantages of the liftgate are the room required behind the vehicle in order to open the liftgate, and the weight of the liftgate itself. Since the liftgate is a single piece basically running from the roof line down to the bumper level, a fairly large amount of clearance is required behind the vehicle in order to provide clearance for the liftgate to swing from a closed position to an open position. This condition often requires the user to move the vehicle away from other vehicles which have been parked behind it so that the liftgate can be opened. The one-piece lifigate also limits how close the vehicle can be parked to an opening (such as a garage door) when items are being unloaded from the cargo area.
Further, since the liftgate is a large single piece unit often incorporating a rear window, a rear window wiper, and a wiper motor, the weight of the liftgate can be considerable. The effect of the weight of the liftgate can be compensated for by providing hydraulic lifts or struts to assist the operator in opening the liftgate. However, the force of the lifts must then be overcome in order to close the liftgate thereby increasing the effort required to lower the liftgate. The struts are generally designed to provide enough lifting force that even if they wear or some of the internal pressure bleeds down over time they will still provide sufficient force to assist in lifting and holding the liftgate in the open position. Therefore, when the struts are new the force which must be overcome can be significant.
Another disadvantage of one-piece liftgates is the height of the liftgate when it is in the open position. Some people find the liftgate handle, which may pivot down when the liftgate is open or may be fixed to the liftgate structure, difficult to reach while at the same time others find that there is insufficient head clearance when they walk underneath the liftgate.
Several disadvantages of the two-piece vertical door systems utilized on cargo vans and full size vans is the physical limitation presented to the vehicle stylist in trying to soften the look of the rear of the vehicle. Fundamental kinematics of the motion of the doors and the hinging required to support the doors limits the tumble home, or slope, a two-piece vertical door system is allowed to have from the roof line to the lower window portion of the vehicle. This lower window portion is often referred to as the belt line of the vehicle. With ever increasing emphasis on reduced coefficient of drag and aerodynamic performance, stylists have tended toward having an increased tumble home at the rear of the vehicle. By utilizing the two full height vertical doors for the rear opening of the vehicle the ability to increase the tumble home is limited. Further, many automotive stylists wish to increase the rear tumble home in order to provide a more aesthetically pleasing side view of the vehicle such that the rear of the vehicle has character lines which are coordinated with the sloping front ends of many new vehicles.